Annex

A.1: Indicators of energy use in agriculture

FAO has initiated work on the development of energy indicators of sustainable agriculture. The definition for the basic indicator is the energy utilized in agriculture on a yearly basis expressed as a ratio of energy inputs and agricultural production as well as in absolute terms. This is measured in unit of Joules per tonne of agricultural products, and its purpose is to provide a measure of energy intensity in agriculture.

The development of this indicator is highly relevant to sustainable development. Energy is essential for most human activities, including agriculture. Too little energy makes it difficult to obtain decent productivity and meet food requirements. Too much energy signifies waste, global warming, and other stress on the environment. The indicator can guide policies and investments regarding (i) energy requirements in all stages of agricultural production in order to measure agricultural productivity and, (ii) energy efficiency, to reduce energy intensity. The indicator is relevant to promote an increase in agricultural production with a parallel increase in energy efficiency. The indicator is closely related to the energy indicators under consumption and production patterns. It is also linked to environmental indicators such as land condition change and emissions of greenhouse gases.

Total energy consumption in agriculture derives from the energy inputs in all stages of agricultural production and processing, that is land preparation, mechanization, fertilization, irrigation, harvesting, transport, processing, and storage. Each of these stages uses different forms of energy (mechanical, electrical, thermal) which can be aggregated in equivalent units. Total agricultural production is an established concept and needs no further elaboration.

Annual energy inputs for each stage in agricultural production and processing are determined

and converted into equivalent units such as terajoules (TJ) and aggregated as total energy. Annual agricultural production figures are collected for all products. The obtained values are then compared for the same year, and can be tracked over time to see how changes in both terms affect their ratio. At present, no international targets exist or apply. At the national level targets could be developed, depending on the country's range of agricultural products.

Agricultural production is affected by factors other than energy inputs (for example, climate, availability of other inputs). These factors are less distorting if comparative values are collected for consecutive years. Data for energy use in agriculture at the present time are not considered to be very reliable. Special surveys could generate sound data, but would be expensive, and may not be a priority for statistical agencies. The indicator could be expanded to include non-commercial energy inputs, such as human and animal power. Human power quantification methodologies might need to be further elaborated. The relevance of this alternative to sustainable development is questionable.

Data are needed on energy inputs for different agricultural activities and on agricultural production. Some data are available for most countries, although reliable and comprehensive statistics to enable time-series analysis are elusive. Energy balances are prepared by energy ministries or other competent national authorities. Agricultural production figures are available from agriculture ministries. FAO has processed and compiled considerable data in both energy and production at the international level.

A.2: Bioenergy terminology and database²⁹

Bioenergy systems are complex and any final energy use can be supplied by different technologies using many kinds of biomass as fuel (Figure A.1). For instance, either sugar (food product) or alcohol (usually for energy) can be produced as a main product from sugarcane, but in both processes an important amount of bagasse is yielded. Bagasse is a solid lignocellulosic by-product, which can be used to produce either heat and electricity by direct combustion, or more alcohol, using acid or enzymatic hydrolysis. Fuelwood can be derived from different sources, both native and planted forests, as well as from by-products of forest industries (sawmills, particle board plants, etc.) and is used by different sectors, such as households, rural industries and commercial activities. This intrinsic complexity is relevant and should be properly considered when a bioenergy database is created.

Figure A.1: Generic Bioenergy System

Table A.1 lists a biofuel classification, which recognizes the basic site where biomass production occurs. The groups on the supply side deal with important sub-divisions, which identify the origin of biofuels. On the user side, a variety of fuels can be produced for each group. Listed on the right side of Table A.1 are the different types and qualities of primary, secondary and even tertiary fuels which can be used for heat, electricity and power generation. The secondary and tertiary fuels are often derived from raw biomass produced from different supply sources after the application of more or less complex transformation processes. Brief definitions of the main terms adopted are listed in Table A.2.

Table A.2: Definition of Biofuel Classifications

Detailed definitions

• Biofuels: organic primary and/or secondary fuels derived from biomass which can be used for the generation of thermal energy by combustion or by using other technology. They comprise both purpose-grown energy crops, as well as multipurpose plantations and by-products (residues and wastes). The term "by-products" includes the improperly called solid, liquid and gaseous residues and wastes derived from biomass processing activities. There are three main biofuel categories: Woodfuels, Agrofuels and Municipal wastes.
• Woodfuels: include all types of biofuels derived directly and indirectly from trees and shrubs grown in forest and non-forest lands. Woodfuels include biomass derived from silvicultural activities (thinning, pruning etc.) and harvesting and logging (tops, roots, branches, etc.), as well as industrial by-products derived from primary and secondary forest industries which are used as fuel. They also include woodfuels derived from ad hoc forest energy plantations. Taking into account the available database, it is interesting to classify woodfuels into four groups: Direct woodfuels, Indirect woodfuels, Recovered woodfuels and Wood-derived fuels, as defined as follows.
• Direct Woodfuels: consists of wood directly removed from Forests (natural forests and plantations; land with tree crown cover of more than 10% and area of more than 0.5 ha);
• Other Wooded Lands (land either with a tree crown cover of 5-10% of trees able to reach a height of at least 5 m at maturity in situ; or crown cover of more than 10% of trees not able to reach a height of 5 m at maturity in situ, and shrub or bush cover); and Other Lands to supply energy demands and includes both inventoried (recorded in official statistics) and non-inventoried woodfuels. Direct woodfuels can be divided into primary and secondary fuels, depending on whether they are directly burned or are converted into another fuel, such as charcoal, pyrolysis gases, pellets, ethanol, methanol, etc.
• Indirect Woodfuels: usually consists of industrial by-products, derived from primary (sawmills, particle boards, pulp and paper mills) and secondary (joinery, carpentry) wood industries, such as: sawmill rejects, slabs, edging and trimmings, sawdust, shavings and chips bark, etc. They preserve essentially the original structure of wood and can be used either directly or after some conversion to another biofuel.
• Recovered Woodfuels: refers to woody biomass derived from all economic and social activities outside the forest sector, usually wastes from construction sites, demolition of buildings, pallets, wooden containers and boxes, etc., burned as they are or transformed into chips, pellets, briquettes, powder, etc.
• Wood-derived fuels: refers to woodfuels produced in the forest sector, which require several thermochemical processes before use. They do not preserve any trace of the original wood's physical structure, as is the case with black liquor and methanol produced from wood.
• Black liquor: is the alkaline-spent liquor obtained from the digesters in the production of sulphate or soda pulp during the process of paper production, in which the energy content is mainly derived from the content of lignin removed from the wood in the pulping process.
• Agrofuels: fuel obtained as a product of agriculture biomass and by-products. It covers mainly biomass materials derived directly from fuel crops and agricultural, agroindustrial and animal by-products.
• Fuel crops: is employed to describe species of plants cultivated on fuel plantations or farms to produce raw material for the production of biofuel. The fuel crops can be produced on land farms (manioc, sugar cane, euphorbia, etc.), on marine farms (algae) or in fresh water farms (water hyacinths). The land-produced fuel crops can also be classified under: sugar/starch crops, oil crops and other energy crops. Sugar/starch crops: are crops planted basically for the production of ethanol (ethyl alcohol) as a fuel mainly used in transport (on its own or blended with gasoline). Ethanol can be produced by the fermentation of glucose derived from sugar-bearing plants (like sugar-cane) or starchy materials after hydrolysis. Oil crops: cover oleaginous plants (like sunflower, rape, etc.) planted for direct energy use of vegetable oil extracted, or as raw material for further conversion into a diesel substitute, using trans-esterification processes. Other energy crops: include plants and specialized crops more recently considered for energy use, such as: elephant grass (Miscanthus), cordgrass and galinggale (Spartina spp. and Cyperus longus), giant reed (Arundo donax) and reed canary grass (Phalaris arundinacea).
• Agricultural by-products: are mainly vegetal materials and by-products derived from production, harvesting, transportation and processing in farming areas. It includes, among others, maize cobs and stalks, wheat stalks and husks, groundnut husks, cotton stalks, mustard stalks, etc.
• Agroindustrial by-products: refer to food processing by-products, such as sugar-cane bagasse, rice/paddy husks and hulls, coconut shells, husks, fibre and pith, ground nut shells, olive pressing wastes, etc.
• Animal by-products: refer to dung and other excreta from cattle, horses, pigs, poultry and, in principle, humans. It can be dried and used directly as a fuel or converted to biogas by fermentation. Biogas: is a by-product of the anaerobic fermentation of biomass, principally animal wastes by bacteria. It consists mainly of methane gas and carbon dioxide.
• Municipal By-products: refer to biomass wastes produced by the urban population and consist of two types of products: solid municipal by-products and gas/liquid municipal by-products produced in cities and villages.
• Solid municipal biofuels: comprise by-products produced by the residential, commercial, industrial, public and tertiary sectors that are collected by local authorities for disposal in a central location, where they are generally incinerated (combusted directly) to produce heat and/or power. Hospital waste is also included in this category.
• Gas/liquid municipal biofuels: correspond to biofuels derived principally from the anaerobic fermentation (biogas) of solid and liquid municipal wastes which may be land-fill gas or sewage sludge gas.

The most commonly used types of woodfuels are fuelwood and charcoal, which can be burned in both traditional and modern energy systems for cooking, heating or power. These main woodfuels can be recognized under this category (fuelwood and charcoal) even when other fuels, such as chips, wood powder, pellets, briquettes, methanol, ethanol, pyrolysis gases, producer gas, etc., can also be derived from the previously mentioned main supply sources.

• Fuelwood: includes "wood in the rough" in small pieces (fuelwood), chips, pellets and/or powder derived from forests and isolated trees, as well as wood by-products from the wood products industry and from wasted wood products. When needed, fuelwood can be prepared into more convenient fuels, such as chips and pellets. Chips: wood that has been deliberately reduced to small pieces from wood in the rough, or residues suitable for energy purposes. Wood pellets: can be considered as a fuel derived from the auto-agglomeration of woody material as the result of a combined application of heat and high pressure in an extrusion machine.
• Charcoal: refers to a solid residue derived from the carbonization, distillation, pyrolysis and torrefaction of wood (from the trunks and branches of trees) and wood by-products, using continuous or batch systems (pit, brick and metal kilns). It also includes charcoal briquettes, made from wood-based charcoal which, after crushing and drying, is moulded (often under high pressure), generally with the admixture of binders to form artefacts of even shapes.

Parameters and Units

Energy sources and commodities may be measured by their mass or weight or still volume, but the essential factor is the energy content related to these sources and commodities. That energy worth must be evaluated in terms of energy parameters, always using standard units. This standardization in the recording and presentation of original units is a primary task of energy and forestry statisticians before quantities can be analyzed or compared. It is recommended that for international reporting, and as far as possible in national accounting procedures, energy and forestry statistics should use the International System of Units, officially abbreviated to SI. Two basic relationships for bioenergy evaluation are introduced as follows, keeping in mind that both the heating value and density depend mainly on the moisture of the biofuel.

(1)

(2)

• Mass: most solid biofuels, such as wood and agrofuels, are measured in units of mass, as are many liquid fuels. The principal units of mass used to measure energy commodities include the kilogram and the metric ton. The metric tonne is the most widely adopted.
• Volume: units of volume are original units for most liquid and gaseous, as well as some solid, fuels (woodfuel, charcoal, etc.). The basic SI units of volume are the litre and the kilolitre, which is equivalent to the cubic metre. The stere or stacked volume, usually considered as equal to 0.65 solid cubic meter, has been widely used in the past when measuring the woodfuel volume. Current preference is to measure timber and fuelwood using solid volume units, usually in cubic meter. One advantage of measurements by volume is the relatively small influence of the moisture content of the wood on the measurement results. The more water per unit weight, the less fuelwood. Therefore, it is imperative that the moisture content be accurately specified when fuelwood is measured by weight.
• Density: the density of wood, i.e., the weight per unit of volume, varies widely between different wood species and types. The density of an air-dried hardwood, such as mahogany or ebony, is around 1 000 kg/cum. The air dried density of a really lightweight wood, such as balsa, is as low as 160 kg/cum. The usual species used for fuelwood are around 500 and 600 kg/cum.
• Moisture: the amount of water in biofuel affects, in a decisive manner, the available energy of every biofuel. Two methods (dry and wet basis) are commonly used to specify the moisture content, depending on the adopted basis used to account for the water mass. It is important to distinguish between them, especially when the moisture content is high.

(3)

(4)

The wet weight refers to the burned condition and the dry weight refers to wood after a standardized drying process. It is important to state on which basis the moisture content is measured.

• Ash content: another important factor of the biofuel energy content is the ash content, always measured on the dry basis, which refers to the solid residue remaining after the complete combustion. While the ash content of fuelwood is generally around 1%, some species of agrofuels can register a very high ash content. This affects the energy value of the biofuels since the substances that form the ashes generally have no energy value. Thus dry woodfuels with a 4% ash content will have 3% less energy than biomass with a 1% ash content.
• Heating value (or calorific value): biofuel is essentially a material for burning as fire or as a thermal source of energy. The amount of thermal energy stored can be measured through the heating value or calorific value of fuels. The higher heating value (HHV), or gross calorific value (GCV), measures the total amount of heat that will be produced by combustion. However, part of this heat will be locked up in the latent heat of the evaporation of any water existent in the fuel during combustion. The lower heating value (LHV), or net calorific value (NCV), excludes this latent heat. Thus, the lower heating value is that amount of heat which is actually available from the combustion process for capture and use. The higher the moisture content of a fuel, the greater the difference between GCV and NCV and the lesser the total energy available, as shown in Figure A.2.

Figure A.2: Effect of moisture (wet basis) on heating value

Charcoal - When statistically recording the conversion from fuelwood (or woodfuels) to charcoal, three principal aspects must be dealt with: wood density, moisture content of the wood, and the means of charcoal production. The yield of charcoal from fuelwood, using different types of kiln, is presented in Table A.3. (165 kg of charcoal is produced from one cubic meter of fuelwood).

Table A.3: Fuelwood required for charcoal production (m³/ton of charcoal)

Agrofuels - The energy values of agricultural by-products are determined by its moisture content and its ash content. Data for these energy sources are rarely collected directly but are derived from crop/waste or end-product/waste ratios. Bagasse is used as a fuel mostly for the sugar industry's own energy needs, but surpluses are sold to the public grid in many sugar-producing countries. Table A.4 presents data for typical agricultural by-products.

Table A.4: Energy data for selected agricultural by-products

The main factors to be used for bioenergy accounting cover several kinds of biofuels and considering the usual information available from primary data sources. The objective here is to obtain the energy worth of a mass or volume flow of some biofuel, so expressions (1) and (2), already presented above, must be used. However, taking into account the substantial variations in heating value and volume with moisture, it is advisable to express the values of biofuels in a dry and without ash basis, especially for accounting in energy balances. Table A.5 presents values for density and the heating value for typical moisture content.

Table A.5: Basic parameters in accounting biofuels

A.3: Recommendations to promote Photovoltaics for Sustainable Agriculture and Rural Development

The following is a package of recommendations arising from the FAO study directed at promoting cooperation between institutions from the energy, agricultural and rural development sectors with the aim to use the opportunities that PV systems offer in contributing to Sustainable Agriculture and Rural Development (FAO, 2000a). These recommendations are the result of an assessment of the experiences collected in this study, enriched with other discussions and inputs. They are intended to provide a set of activities for different stakeholders involved in the process of PV electrification and rural development. It is clear that the main responsibility for action lies with national development authorities. The role of technical cooperation agencies such as FAO is to support these national efforts.

Policy and planning

• National governmental policies need to be established to promote the important role that renewable energies in general, and solar photovoltaic systems, in particular, can play in achieving sustainable agriculture and rural development;
• these policies should guide the establishment of plans, programmes and targets of the agricultural, energy and environmental sectors, and should also create the appropriate environment and the necessary regulatory and normative context for the role of the private sector and non-governmental institutions;
• synergies as identified when PV applications are promoted simultaneously in various sectors of rural society, should be built into policies and programmes;
• policies in the electricity sector should establish the role of independent power producers and the rules to be followed by both power producers and purchasers;
• policies and programmes should also establish the nexus with international efforts to reduce CO₂ emissions and fulfil the goals and targets of the Climate Change Convention and the Kyoto Protocol;

Research and development

• Research is further needed to assess the replicability of promising PV applications and the conditions under which they are successful;
• further research efforts are required for the optimization of PV systems for agricultural use (panels, electronics, applications and end-uses), in order to develop optimized services or product packages, e.g. optimized irrigation systems (panels, electronics, pumps and drip-irrigators) for economic irrigation and fertilization;
• such efforts should be accompanied by assessment of the life cycle technical and economic behaviour of theses PV systems, and by the development of accompanying training and dissemination programmes;
• other areas of continued research and development are low energy consuming appliances (such as affordable low energy consumption refrigerators) and PV/diesel and PV/wind hybrid energy systems;
• research should also include the development of quality standards, e.g. for agricultural applications, in combination with mechanisms to implement these standards;

Finance

• Rural and agricultural development banks should include PV systems as eligible for loans;
• innovative financing channels should be explored, including the possibility of applying the CDM to PV systems; it is expected that investments in productive uses (agriculture) of PV will be easier to finance than Solar Home Systems because of the income generated by the former;
• as for many other products, equal access to credit by women is required, which would increase their chances to use PV for household and income generating opportunities;
• private sector investments can and should be attracted for financing of PV electrification programmes; international donor funds, soft terms loans and other seed capital can be used as a leverage for such private sector investments.

Demonstration, implementation and marketing

• Demonstration and promotion are required for PV applications such as drip-irrigation, cattle watering, PV electric fences and aquaculture applications, to be integrated in agricultural development programmes;
• demonstration and promotion of small PV systems for small cottage industry activities are needed to increase the awareness and knowledge of PV contribution to micro-enterprise development. A possible and innovative approach could be based on PV powered micro-enterprise development zones or business incubator, through the installation of multi-purpose or multi-service PV units, that can deliver power for income generating activities and common access to phone/fax/web;
• demonstration projects, not done in isolation, but as an intrinsic component of an implementation plan, should include all main stakeholders, including the private sector and government; results of these demonstration efforts should be made public;
• subsidies, when necessary, should be transparent, targeted and time-framed within a gradual phase-out plan; otherwise subsidies should be limited to those PV applications for basic social services such as education, health care, etc.;

Training/information/education/awareness

• Agriculture and other rural extension services should become agents to identify potential PV applications; information and training in this field is required;
• training packages are required for preparing PV installation, operation, maintenance and repair services, but also in the use of PV for various agricultural applications, e.g. improved irrigation techniques;
• particular attention should be given to information and training of women, as main users especially of household systems, and academic curricula at all levels should be prepared and incorporated into educational programmes.

Institutions

• The complex institutional set-up behind SARD needs to be "energized" by the institutions dealing with energy, in general, and with PV systems, in particular;
• to this end, intersectoral efforts are required to bring closer the plans, programmes and policies identified above; this involves the agriculture, energy, health, education and environmental sectors in particular;
• such intersectoral collaboration is critical since small renewable energy systems can have a significant and durable impact on rural development if applied in "packages" in, for instance, agriculture and social services (e.g. communication, education, health care);
• synergies as identified when PV applications are promoted simultaneously and in an integrated approach in various sectors should be built into collaborative implementation and marketing strategies;
• there is a scope for developing a plan for action for the integration of rural energy delivery programmes with micro-enterprise development programmes; mutual benefits could be gained: PV electricity rural markets can become a source and stimulus for both Energy Service Companies and for small "electrified" entrepreneurial activities;
• since PV systems normally require more involvement of the end-user than conventional grid electricity, the involvement of farmers' and other end-users' organizations in all phases of PV programme design and implementation is critical; failure to achieve ownership will most probably lead to failure of the programme.

²⁹ Source: FAO proposal under discussion, (FAO, 2000d).